Right now, parallel camera has no specific position along Z axis, all nodes are rendered regardless of how far they are translated into negative values along Z axis. For picking this means:
* We support "bidirectional pick ray", which picks also nodes "behind" the pick ray origin
* PickResult for parallel camera contains always distance=infinity
We need to define if this is the way we want it. If so, this issue can be closed. In case we want to change the parallel camera to have a specific position and render only nodes in front of it, we can remove the bidirectional pick ray feature and we can also report the concrete distance.

This should be resolved as soon as possible because it affects public API.